Question

A bus running at a speed of $18km/hr$ is stopped in $2.5sec$ by applying brakes. Calculate the retardation produced.

Answer 1

Step 1: List the given values

Given, the initial velocity of the bus, $v_i=18km/hr$

We know that $1km/hr=\frac{5}{18}m/s$

$\therefore 18km/hr=\left(\frac{5}{18}\times 18\right)m/s$

$=5m/s$

The final velocity of the bus $v_f=0$ since the bus comes to rest

The time taken $t=2.5s$

Step 2: Calculate the retardation

We know that acceleration,

$a=\frac{v_f-v_i}{t}$

$=\frac{0-5}{2.5}$

$=-2m/s^2$

We know that retardation is the negative of acceleration.

$a_r=-a$

$\therefore a_r=2m/s^2$

Hence, the required retardation is $2m/s^2$.